Background: Although prehypertension is known to be associated with an increased incidence of cardiovascular disease, there are few population-based studies on alterations in left ventricular (LV) structure and function among individuals with prehypertension. The aim of this study was to evaluate the effects of normal blood pressure, prehypertension, and hypertension on LV structure and function. Methods: subjects were drawn from the Korean Health and Genome study, which is an ongoing population-based prospective study of Korean adults aged 40 to 69 years. The sample comprised 452 men and 732 women without known cardiovascular disease. LV structure and function were assessed by two-dimensional echocardiography and tissue Doppler imaging (TDI). With TDI, systolic velocity (Sa), early (Ea), and late diastolic (Aa) velocities were measured at the mitral septal annulus. Results: Prehypertension and hypertension subjects were more often men (47% and 43% versus 33%), older age (54 and 56 versus 53 years), more commonly diabetic (19% and 25% versus 12%), more alcohol drinker (52% and 48% versus 39%) than normal blood pressure participants. There were no significant differences in systolic parameters such as ejection fraction and Sa among the three groups. However, subjects with prehypertension and hypertension had higher LV mass index (90 and 94 vs. 85 g/���, p < 0.001) and LV filling ratio (E/Ea) (10.4 and 10.9 vs. 9.5, p < 0.001), whereas Ea (6.7 and 6.6 vs. 7.5cm/s, p < 0.001) and Ea/Aa ratio (0.8 and 0.8 vs. 0.9, p < 0.001) were significantly reduced compared with normal blood pressure subjects. In a multivariate linear regression analysis, prehypertension as well as hypertension remained a significant predictor of LV Ea even after adjusting for covariates (all p < 0.001). Conclusions: These findings show that the alterations in LV structures and function are already initiated at the stage of prehypertension, not hypertension. More aggressive interventions to regress and/or prevent the progression of changes in LV geometry and function are warranted.